The present invention relates to an image output system and, more particularly to an improved image output system wherein a high speed processing time in an image output apparatus as a whole can be attained and a lifetime decrease of a printer means of the image output apparatus can be restrained to the utmost. Such an image output apparatus is, for example, an interface controller for use in a laser beam printer.
An external appearance of an image output apparatus in which an image output system is applied to will be explained referring to FIG. 4. In FIG. 4, a data source 1 and an image output apparatus 2 are connected with a signal conductor. The image output apparatus 2 and a page printer 3 as a printer means are connected also with a signal conductor. Such a page printer 3 has one page buffer at the least.
FIG. 5 is a block diagram of an image output apparatus in which a first conventional image output system is adopted, and FIG. 6 is a processing flow-chart of the image output apparatus shown in FIG. 5.
In FIG. 5, the image output apparatus 2 comprises mainly a central processing unit (CPU) 4 and a page buffer memory member 6 in which picture element data 9 having one page part is stored. The central processing unit 4 has a function that a code data 7 received from the data source 1 is developed as the picture element data 9 and the developed picture element data 9 is stored in the page buffer memory member 6. The central processing unit 4 further has a function that the picture element data 9 stored in the page buffer memory member 6 is outputted into the page printer 3.
As shown in FIGS. 5 and 6, the image output apparatus 2 receives the code data 7, for example character code data for one code data part. The character code data is such as an Ascii code or Japanese Industrial Standard (JIS) code etc.. The code data 7 received by the image output apparatus 2 is converted to the picture element data 9, which is an assembly of a plurality of dots, by the central processing unit 4 and stored in the page buffer memory member 6 in order from the forefront. The central processing unit 4 carries out repeatedly these processing operations so far as to receive a control code data which indicates one page part finishing (end).
When one page part development is finished, a printing process preparation signal (PRREQ) 10 is outputted to the page printer 3. When the printing process preparation signal (PRREQ) 10 is outputted, the page printer 3 prepares a printing process. When the preparation for the printing process is completed, a synchronous signal require signal (VSREQ) for requiring a synchronous signal 11 is outputted to the image output apparatus 2 and waits for a synchronous signal (VSYNC) 12 from the image output apparatus 2.
In order to operate the preparation for the printing process, it requires a time of about from several seconds to more than ten seconds in the ordinary page printer When the image output apparatus 2 receives the synchronous signal require signal (VSREQ) 11 from the page printer 3, the synchronous signal (VSYNC) 12 is transmitted to the page printer 3 and a line for one page part of the picture element data 9 in the page buffer memory member 6 is transmitted to the page printer 3 as a printing data signal (VIDEO) 13. Thus, the image output processing for one page part is completed.
FIG. 7 is a block diagram of an image output apparatus which adopts a second conventional image output system different from the image output apparatus shown in FIG. 5. FIG. 8 is various signal timing-charts of the image output apparatus shown in FIG. 7, and FIG. 9 is a processing flow-chart of the image output apparatus shown in FIG. 7.
In FIG. 7, a data source 1 and an image output apparatus 2 are connected with a signal conductor, and also the image output apparatus 2 and a page printer 3 are connected with a signal conductor. The image output apparatus 2 comprises mainly a central processing unit (CPU) 4 and a page buffer memory member 6 for storing picture element data 9 for one page part. The image output apparatus 2 receives code data 7 outputted from the data source 1 as shown in FIGS. 7-9.
Immediately after the image output apparatus 2 receives a first code data (ID) from the data source 1, the printing process preparation signal (PRREQ) 10 is outputted to the page printer 3, thereafter a control code data indicating one page part finishing is developed with the picture element data 9 and stored in the page buffer memory member 6.
When the development processing for one page part is finished, a synchronous signal require signal (VSREQ) 11 is waited for receipt thereof from the page printer 3. After the synchronous signal require signal (VSREQ) 11 is received, a synchronous signal (VSYNC) 12 is transmitted to the page printer 3 and one page part of the picture element data line in the page buffer memory member 6 is transmitted as a printing data signal (VIDEO) 13. Thus, the image output processing for one page part is completed.
According to this second conventional image output system, the printing process preparation processing and the development processing of the code data 7 are carried out together, therefore a high speed processing time of the image output apparatus 2 as a whole can be attained in comparison with the above stated first conventional image output system.
FIG. 10 is a block diagram of an image output apparatus which adopts a third conventional image output system different from the image output apparatus shown in FIG. 5 and FIG. 7, and FIG. 11 is a processing flow-chart of the image output apparatus shown in FIG. 10.
In FIG. 10, a data source 1 and an image output apparatus 2 are connected with a signal conductor, and also the image output apparatus 2 and a page printer 3 are connected with a signal conductor. The image output apparatus 2 comprises mainly a central processing unit (CPU) 4, an intermediate code buffer memory member 5, and a page buffer memory member 6.
The central processing unit 4 functions that code data 7 is received from the data source 1 and converted to intermediate code data 8, the intermediate code data 8 is converted to picture element data 9, and further the picture element data 9 is outputted into the page printer 3. The intermediate code buffer memory member 5 stores the intermediate code data 8 which is converted from the code data 7 by the central processing unit 4. The page buffer memory member 6 stores the picture element data 9 which is converted from the intermediate code data 8 by the central processing unit 4.
In FIGS. 10 and 11, when the image output apparatus 2 receives the code data 7 from the data source 1, the code data 7 is converted to the intermediate code data 8 by the central processing unit 4 and stored in the intermediate code buffer memory member 5. These processes are carry out repeatedly so far as to receive a control code data which indicates one page part finishing of the transmitted code data 7.
After the picture element data 9 for a previous page part, which is one page part just before a present page, received in the page buffer memory member 6 is outputted to the page printer 3, the intermediate code data 8 for one page part is converted to the picture element data 9. After the picture element data 9 is stored in the page buffer memory member 6, the printing process preparation signal (PRREQ) 10 is outputted to the page printer 3. The subsequent processing is carried out similar to the above stated first conventional image output system.
According to this third image output system, in case of continuous plural pages printing, even if the picture element data 9 for the previous page part, which is one page part just before the present page part, is not inputted and remains still in the page buffer memory member 6, the code data 7 for the present page part can be developed and processed as the intermediate code data 8 which is a code data just before being converted as the picture element data 9.
In case of the picture element data 9 for the previous page part received in the page buffer memory member 6 is outputted to the page printer 3, it is possible to develop promptly the code data 7 for the present page part as the picture element data 9. Therefore a high speed processing time of the third conventional image output system as a whole during a continuous printing can be attained in comparative with the above stated first conventional image output system.
However, in the first conventional image output system, the development processing of the code data 7 outputted from the data source 1 and the printing process preparation processing of the page printer 3 carries out entirely to be in a row, so that there is problem that a long time processing in the image output apparatus 2 as a whole is required.
In case of the above stated second conventional image output system, the printing process preparation processing in the page printer 3 and the development processing of the code data 7 in the image output apparatus 2 can carry out together, however, when a data transfer frequency from the data source 1 is low or the control code data indicating one page part finishing does not reach, the page printer 3 must wait for a long time keeping at the printing process preparation condition.
The page printer 3 may adopt commonly an electro-photo system as a printing method. When the electro-photo system is adopted as the printing method, under the printing process preparation condition, the discharge breakdown action by the corona discharge, the friction action by the cleaning mechanism, and the light fatigue action by the photo-scanning remain to be added to the electro-photosensitivity member being as a heat portion in the page printer 3, therefore there is problem that the lifetime of the electro-photosensitivity member becomes short remarkably.
Further, in the third conventional image output system, under the continuous plural pages printing, even if the picture element data 9 for the previous page part is not inputted and remains still in the page buffer memory member 5, the code data 7 for the present page part can be developed and processed as the intermediate code data 8 which is a code data just before being converted as the picture element data 9. When the picture element data 9 for the previous page part received in the page buffer memory member 5 is outputted, the code data 7 for the present page part can be developed promptly as the picture element data 9.
However, the development processing of the code data 7 and the printing process preparation processing carry out entirely to be in a row, so that there is problem that a long time processing in the image output apparatus 2 as a whole is required. Therefore, a high speed processing time in the image output apparatus 2 is obstructed.
Such a conventional technique about the image output system is shown in, for example in Japanese Patent Laid-Open No. 178870/1984.